In an electricity grid, the electricity is produced at very high voltage and injected into a transmission network. An electricity transmission network typically consists of high voltage circuits that supply power to transformer substations that step down voltage progressively until delivering this power via distribution networks to the household or building.
The electricity distribution network generally comprises a system having two parts, primary and secondary. The primary distribution system consists of overhead lines or underground cables, which are called feeders. The feeders run along the streets and supply the Low Voltage Transformers (LVT) that step the voltage down from the primary level (2.4-34.5 kV) to the secondary level (120-480 V). The secondary distribution system contains overhead lines or underground cables that connect the LVTs and the consumer households. Usually an LVT powers up to about 200 households and each of those households gets connected to a single phase (A, B or C). In a three-phase system, three feeders carry three alternating currents (of the same frequency) which reach their instantaneous peak values at different times.
Smart grids refer to electricity grids (ranging from generation, transmission, distribution or customer domains) that are increasingly instrumented, allowing them to achieve higher levels of observability and controllability for various economic or policy purposes. Automated monitoring and control in electricity grids has traditionally been done in the high voltage transmission network portion of the grid. More recently the medium and low voltage networks have begun to be instrumented with intelligent monitoring and control devices that report in real-time on the electrical behavior of the network. Energy distributors have commenced upgrades of manually read analogue household meters with automated smart meters that communicate meter readings with greater frequency back to the distributors. These initiatives form the basis of many smart grid transformations that energy distributors are undertaking, and in turn, result in an expectation of better understanding of long-term, intractable problems related to electricity grids.